Electric heating – Metal heating – Of cylinders
Patent
1979-09-11
1982-08-17
Reynolds, B. A.
Electric heating
Metal heating
Of cylinders
H05B 668
Patent
active
043451349
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a composite heating apparatus capable of providing dielectric heating with high frequency energy, and resistance heating for heating and cooking by increasing the ambient temperature in a single heating chamber to a high temperature.
BACKGROUND OF THE INVENTION
A conventional composite heating apparatus of this type is commercially produced in which the high frequency and resistance heating are operated separately, or the resistance heating is switched automatically to heating by high frequency energy. In either type, the cooking effect obtained by simultaneous dielectric heating in which the food is heated from within and resistance heating in which the food is heated from the outside cannot be expected. Even if there would be available a composite heating apparatus capable of dielectric heating and resistance heating simultaneously, simultaneous operation of a high frequency heating apparatus of the electric capacity of, say, 1.2 KW and a resistance heating apparatus of 1.2 KW would result in a current of about 24 A flowing in an ordinary home supplied with a source voltage of 100 V, thus posing the problem that such an apparatus cannot be used due to power consumption limitations in areas having unfavorable power supply situations. Such an apparatus requires a power supply and power equipment of a large capacity, and is difficult to commercialize. Further, the simultaneous operation of both large output heaters is not desirable from the viewpoint of cooking effects and energy saving.
SUMMARY OF THE INVENTION
Accordingly, this invention makes possible cooking by simultaneous heating together with use in an area having unfavorable power supply conditions by appropriately controlling the high frequency dielectric heating output and resistance heating according to the type of food. An embodiment of the present invention will be described below with reference to the attached drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a general perspective view of a high frequency heating apparatus according to an embodiment of the present invention,
FIG. 2 is an electrical circuit diagram of the same apparatus,
FIG. 3 is a diagram showing the relations among the input, heating time and temperature in the chamber in the same apparatus, and
FIG. 4 is a diagram showing a relationship obtained with prior art apparatus corresponding to FIG. 3.
BEST MODE FOR CARRYING OUT THE INVENTION
In FIGS. 1 and 2, 1 shows a time switch operated by a timer motor 2. 3, 4 and 5 show power relays, in which 4 shows a power relay for actuating a high frequency generator 6, 5 a power relay for cutting off a heater 8 connected in parallel with a heater 7, thus switching the output of the heating apparatus from a strong to a weak state, and 3 a power relay for interrupting both circuits. In other words, upon depression of an operating switch 10 when a door switch 9 is closed, a coil of the power relay 3 is excited, thus turning on the power relay 3. Once power is supplied to the coil, a self-holding circuit is formed, so that power continues to be supplied even after the operating switch 10 is turned off. If the door switch 9 is turned off, however, the self-holding circuit is released, thus turning off the power relay 3. A self-holding circuit is formed in a similar fashion in the power relays 4 and 5 as in the power relay 3.
Next, an embodiment of the temperature control means in this apparatus will be explained. 11 shows a full-wave rectifier circuit. The rectified current flows to a bridge circuit 14 through a smoothing resistor 12 and a capacitor 13. 15 shows a comparator. As shown in the drawing, when the voltage at point A of the bridge circuit is reduced below the voltage at point B, a current flows in the transistor 16, thus exciting a coil 17 of the relay. In other words, power is supplied to the coil 17 when the relation ##EQU1## is established among the resistors R.sub.1, R.sub.2, R.sub.3, R.sub.4 and a thermistor S. Thus, when the thermistor S in the heating chamber (not shown)
REFERENCES:
patent: 3320396 (1967-05-01), Boehm
patent: 3569656 (1971-03-01), White et al.
Orita Masatomo
Tanaka Junzo
Leung Philip H.
Matsushita Electric - Industrial Co., Ltd.
Reynolds B. A.
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